FUNCTION: [Summary is not available for the mouse gene. This summary is for the human ortholog.] The protein encoded by this gene is a member of the TNF-receptor superfamily. This receptor contributes to the clonal expansion, survival, and development of T cells. It can also induce proliferation in peripheral monocytes, enhance T cell apoptosis induced by TCR/CD3 triggered activation, and regulate CD28 co-stimulation to promote Th1 cell responses. The expression of this receptor is induced by lymphocyte activation. TRAF adaptor proteins have been shown to bind to this receptor and transduce the signals leading to activation of NF-kappaB. [provided by RefSeq, Jul 2008] PHENOTYPE: Homozygous mutation of this gene results in enhanced T cell proliferation, decreased B cell IgG production, decreased cytotoxic T cell activity, and increased numbers of erythrocytes, granulocyte macrophages, and multipotential progenitor cells in the bone marrow, blood, and spleen. [provided by MGI curators]